Complex Structures: Mastery Test

1. Select the correct answer.
What is the chemical name of the compound [tex]\( Na_2CO_3 \)[/tex]?

A. sodium carbon oxide
B. sodium carbonate
C. sodium(II) carbonate
D. sodium oxalate

Use the list of polyatomic ions and the periodic table to help you answer.

[tex]\[
\begin{array}{|c|c|}
\hline \text{Chemical Name} & \text{Chemical Formula} \\
\hline \text{nitrite} & NO_2^- \\
\hline \text{ammonium} & NH_4^+ \\
\hline \text{cyanide} & CN^- \\
\hline \text{hydroxide} & OH^- \\
\hline \text{peroxide} & O_2^{2-} \\
\hline \text{phosphate} & PO_4^{3-} \\
\hline \text{hydrogen phosphate} & HPO_4^{2-} \\
\hline \text{dihydrogen phosphate} & H_2PO_4^- \\
\hline \text{sulfate} & SO_4^{2-} \\
\hline \text{hydrogen sulfate} & HSO_4^- \\
\hline
\end{array}
\][/tex]



Answer :

To determine the correct chemical name of the compound [tex]\( Na_2CO_3 \)[/tex], we need to break down the components of the formula and then use this information to identify the proper name.

1. Identify the Cation:
- The symbol [tex]\( Na \)[/tex] represents sodium.
- Sodium is a Group 1 element and typically forms a +1 charge as [tex]\( Na^+ \)[/tex].

2. Identify the Anion:
- The symbol [tex]\( CO_3 \)[/tex] represents the carbonate ion.
- Carbonate is a polyatomic ion with the formula [tex]\( CO_3^{2-} \)[/tex].

3. Combine Cation and Anion:
- The compound [tex]\( Na_2CO_3 \)[/tex] consists of two sodium ions ([tex]\( 2 \times Na^+ \)[/tex]) and one carbonate ion ([tex]\( CO_3^{2-} \)[/tex]).
- The charges balance out because [tex]\( 2 \times (+1) \, \text{from sodium} = +2 \)[/tex] and [tex]\( -2 \, \text{from carbonate} \)[/tex].
- The overall charge of the compound is neutral.

4. Naming the Compound:
- The name of the compound is derived from the constituent ions. The cation (sodium) comes first, and the anion (carbonate) follows.
- Hence, [tex]\( Na_2CO_3 \)[/tex] is named sodium carbonate.

5. Verify Against Given Options:
- A. Sodium çarbon axide: Incorrect spelling and chemical structure.
- B. Sodium carbonate: Correct based on the analysis.
- C. Sodium(II) carbonate: Incorrect oxidation state indication for sodium which is not needed here as sodium typically forms a +1 charge.
- D. Sodium oxalate: Incorrect because [tex]\( Na_2CO_3 \)[/tex] is carbonate, not oxalate (which would be [tex]\( C_2O_4^{2-} \)[/tex]).

Therefore, the correct answer is:

B. sodium carbonate